The main intentions of this program are to identify the immune responses which occur during the immunopathology resulting from schistosoma infection, and to identify and understand the regulatory mechanisms which control these responses. The primary points of interest will continue to be the schistosome egg-induced granulomatous process and the responses against the egg-derived antigenic preparation (SEA). Some studies will be done in parallel using the worm (adult) antigenic preparation SWAP, and their emphasis will be to determine if immunoregulatory mechanisms are mustered upon chronic exposure to this material during infection. If so, these processes may play a role in the evasion, by the worm, of host defense mechanisms. Studies are now focused on suppressor T lymphocytes and serologically-mediated suppressor effects. Both have been identified in our system. The interactions of schistosome eggs and the eosinophils seen in close contact with them within the granulomas will continue to be analyzed. This is to provide information as to the functions of these enigmatic, but increasingly interesting cells. The involvement of lymphokine activation of eosinophils will be pursued. These studies may apply to a wide variety of immunologically-related questions concerning the inter-relationships between initiator and effector mechanisms. Acute schistosomiasis will be analyzed both morphologically and immunologically, in hopes of understanding whether such acute, egg-centered or periportal area-centered, lesions may contribute to the subsequent chronic damage observed.